1. Field of the Invention
The present invention relates to a developing apparatus that performs a development process on a substrate having a resist coated thereon and the resist exposed to light, and a developing method and a storage medium therefor.
2. Description of the Related Art
During a photoresist process that is one of semiconductor-manufacturing processes, a resist pattern is formed on semiconductor wafers (hereinafter, referred to simply as wafers) by coating the wafer surface with a resist and exposing the resist to light in the desired pattern, followed by development. Such a process is usually performed using a system that includes a coating and developing apparatus that performs a coating and development process and an exposure apparatus connected to the coating and developing apparatus.
The coating and developing apparatus includes a developing module (developing apparatus) that supplies a developer onto a wafer having a resist coated thereon to develop the wafer. The developing module includes a substrate holder and a developing unit. The substrate holder holds the wafer. The developing unit has a liquid discharge unit, a gas discharge unit and a cup body. The cup body surrounds the wafer held by the substrate holder. The developing module also includes a developer supply nozzle and a pure water supply nozzle. The developer supply nozzle supplies a developer onto the wafer, and the pure water supply nozzle supplies pure water onto the wafer.
The following briefly describes a process to be performed by the developing apparatus. First, the pure water supply nozzle supplies pure water onto a central portion of the surface of the wafer rotating about a vertical axis through the substrate holder. The pure water spreads toward a peripheral edge portion of the surface of the wafer from the central portion of the surface of the wafer under the centrifugal force of the rotating wafer. In this way, a pre-wetting process is performed to make the surface of the wafer wet in order to improve wettability of the surface of the wafer with the developer that is used in a development process. In the pre-wetting process, a developer may be used instead of the pure water. In such a case, the developer is used not for development but for improvement in wettability of the surface of the wafer with the developer when a liquid film is formed.
Recently, an exposure apparatus that performs immersion exposure has been widely used. With this trend, a resist having a higher water-repellent property has been used in order to suppress an effect of a liquid used for immersion exposure. When such a resist having a high water-repellent property is to be developed, due to surface tension of the developer or pure water, the developer or pure water tends to gather in a region having high wettability on the surface of the wafer during the pre-wetting process and liquid film formation.
Specifically, when the pre-wetting process starts and the pure water spreads from a central region of the surface of the wafer to a peripheral edge portion thereof, wettability in a region that is wet with the pure water on the surface of the wafer is improved. However, wettability in a region to which the pure water is not supplied on the surface of the wafer is low. Once a region having high wettability is formed on the surface of the wafer, the pure water will move to the region having high wettability with the pure water due to the surface tension of the pure water even if the pure water is further supplied onto the surface of the wafer. Then, the pure water will pass through the region having high wettability with the pure water and fall out of a peripheral edge portion of the wafer. As a result, a region having low wettability with the pure water does not become wet with the pure water, ending the pre-wetting process. Next, when the developer is supplied after termination of the pre-wetting process, although the developer spreads to the region having high wettability, the developer does not spread to the region having low wettability due to the surface tension of the developer, as is the case with the pure water supplied in the pre-wetting process. Thus, the region having low wettability in question is not subjected to development process.
The size of the wafer tends to be increased in order to improve the throughput and a 450 mm diameter wafer is studied nowadays. When such a large wafer is used, the wafer may have many regions to which a developer is not applied, resulting in possibly development failure.
Instead of a process for supplying a developer onto the surface of a rotating wafer, the following developing method may be performed. A developer nozzle having a slit-like port, which extends across the diameter of a wafer, supplies a developer onto the surface of the wafer while moving from one end to the other end of the wafer that is in a stationary state so that a liquid film made of the developer is formed on the wafer. After that, the wafer is kept stationary. However, when a resist is highly water-repellent, it may be difficult to uniformly form the liquid film for the aforementioned reasons even when this developing method is used.
In order to uniformly form a liquid film on the wafer, increasing the amount of the developer to be supplied onto the wafer may be adopted. This scheme, however, increases the time for the development process, resulting in reduced throughput and high cost.
Although JP-A-2000-232058 describes a developing apparatus that sprays an atomized developer, it does not discuss the problems described above; therefore such problems cannot be solved.